Guild Wars 2

These runes would add new effects to your weapon skills such as:
-exploding Ice behind Warrior whirlwind attack skill
-necromancer minions explode after dieing if enemy is X units away from the necro or some other conditions.
-decrease channel time of rapid fire( keeping amount of arrows the same).
-Dancing dagger can steal life per enemy hit or heartseeker can kd if hit from X distance (Basically full leap)Cannot repeat for another X seconds.
-Mighty blow(hammer on Guardian) can have a chance to kb.
-Jump shot can daze foes where you land.
-Illusionary wave can fear instead of kb since either way they run away from you but I think depending on the duration, fear sends you further back.

Theres endless combinations that can make “new skills” without just tossing new ones into the batch and getting out of hand.